Olefination Reaction Research Articles

Photoinduced Cobalt Catalyzed Radical Heck-Type Reaction of Alkyl Electrophiles.

We report here a general alkylation reaction of terminal alkenes with nucleophilic cobaloxime complex catalysis under visible light irradiation. A broad range of vinyl arenes and heteroarenes, as well as a diverse set of alkyl(pseudo)halides or strained rings as alkyl electrophiles, can efficiently undergo the transformation up to the gram scale. Mechanistic study reveals the radical nature of the reaction and corroborates our design involving alkylcobaloxime as the key intermediate.

Palladium‐Catalyzed S‐Allylation of Vinyl Carbinols – Total Syntheses of Carotenoids by Julia‐Kocienski Olefination

AbstractPalladium catalyzed S‐allylation of vinyl carbinols from ionones (or conjugated carbonyls) with 2‐mercapto‐1,3‐benzothiazole (BT‐SH) provides versatile C15 dienyl benzothiazolyl (BT) sulfides. This Pd(dppe)Cl2‐catalyzed S‐allylation is highly selective for free allylic alcohols in the presence of allylic acetates, resulting in 3‐ or 4‐acetoxy C15 dienyl BT‐sulfides suitable for xanthophyll synthesis. The corresponding C15 dienyl BT‐sulfones undergo Julia‐Kocienski olefination reactions with C10 2,7‐dimethyl‐2,4,6‐octatrienedial under mild conditions to produce carotenoids natural products. Efficient synthesis is achieved for a range of carotenoids including xanthophylls such as iso‐zeaxanthin, zeaxanthin, and lutein as well as carotenes like β‐carotene, ϵ‐carotene, and 9′‐Z‐phenyl‐carotene.

A CoFe Bimetallic Catalyst for the Direct Conversion of Syngas to Olefins

Syngas conversion is a useful technology for converting nonpetroleum carbon resources into chemicals such as olefins. Iron- and cobalt-based catalysts, as two major categories, have been extensively studied in Fischer–Tropsch synthesis to olefins (FTO) reactions. Although both iron and cobalt catalysts have shown distinct merits and shortcomings, they are also complementary in their properties and catalytic performances when combined with each other. Herein, Na-modified CoFe bimetallic catalysts were fabricated using a co-precipitation method. It was found that there was a synergistic effect between Co and Fe that promoted a CO dissociation rate and carburization, and an appropriate Co/Fe ratio was conducive to improvements in their catalytic performances. The desired olefins selectivity reached 66.1 C% at a CO conversion of 37.5% for a Co2Fe1 catalyst, while the methane selectivity was only 4.3 C%. In addition, no obvious deactivation was found after nearly 160 h, indicating their potential industrial application.

Unusual Kinetics Induced by Ligands in Rhodium(III)-Catalyzed Dehydrogenative Olefination Reactions.

In this study, we investigate the effects of ligands on C-H activation during rhodium(III)-catalyzed C-H bond olefination reactions using well-defined [CpXRhIII] catalytic systems with three representative CpX (Cp (η5-C5H5), CpCF3 (η5-C5Me4CF3), and Cp* (η5-C5Me5)) ligands. Our results demonstrate that C-H activation as the rate-limiting step is significantly influenced by the steric properties of the CpX ligands. Moreover, we observe a dramatic acceleration of the simple [CpRhIII]-catalyzed C-H olefination reaction with acid coproducts such as HOAc, implying an autocatalytic C-H activation process.

Purple‐Light Promoted Thiol‐ene Reaction of Alkenes

AbstractHere we present a catalyst‐free protocol for the purple light‐mediated anti‐Markovnikov functionalization of alkenes with thiols. Crucial to the generation of the thiyl radical was the formation of a key photo‐active complex. More than 30 thioether products were obtained, demonstrating tolerance towards different functional groups and scalability up to 5 mmol of alkene. Two different reaction conditions have been developed, varying both the solvent and the amount of thiol. Depending on the alkene structure, water can be used as an alternative to dichloromethane as a solvent, thus increasing the sustainability of the whole process.

The atmospheric oxidizing capacity in China – Part 1: Roles of different photochemical processes

Abstract. Atmospheric oxidation capacity (AOC) characterizes the ability of the atmosphere to scavenge air pollutants. However, the processes involved in China, where anthropogenic emissions have changed dramatically in the past decade, are not fully understood. A detailed analysis of different parameters that determine the AOC in China is presented on the basis of numerical simulations performed with the regional chemical–meteorological Weather Research and Forecasting model with Chemistry (WRF-Chem). The model shows that the aerosol effects related to extinction and heterogeneous processes produce a decrease in surface ozone of approximately 8–10 ppbv in NOx-limited rural areas and an increase of 5–10 ppbv in VOC-limited urban areas. In this latter case, the ozone increase is noticeable for aerosol concentrations ranging from 20 to 45 µg m−3 in July 2018. The ozone reduction in NOx-sensitive regions is due to the combined effect of nitrogen dioxide and peroxy radical uptake on particles and of the light extinction by aerosols, which affects the photodissociation rates. The ozone increase in VOC-sensitive areas is attributed to the uptake of NO2 by aerosols, which is offset by the reduced ozone formation associated with HO2 uptake and with aerosol extinction. Our study concludes that more than 90 % of the daytime AOC is due to the reaction of the hydroxyl radical with VOCs and carbon monoxide. In urban areas, during summertime, the main contributions to daytime AOC are the reactions of OH with alkene (30 %–50 %), oxidized volatile organic compounds (OVOCs) (33 %–45 %), and carbon monoxide (20 %–45 %). In rural areas, the largest contribution results from the reaction of OH with alkenes (60 %). Nocturnal AOC is dominantly attributed to the reactions with the nitrate radical (50 %–70 %). Our results shed light on the contribution of aerosol-related NOx loss and the high reactivity of alkenes for photochemical pollution. With the reduction in aerosols and anthropogenic ozone precursors, the chemistry of nitrogen and temperature-sensitive VOCs will become increasingly important. More attention needs to be paid to the role of photodegradable OVOCs and nocturnal oxidants in the formation of secondary pollutants.

QM:QM studies on the mechanisms of interaction of alkenes with zeolitic Brønsted sites in H-FER

The chemically accurate hybrid MP2:(PBE + D2) + ΔCCSD(T) method is used to search the transition states for five reactions of alkenes with the Al(2)O(7) Brønsted acid site in H-ferrierite (H-FER). The relative energy barriers for the alkene adsorption on Brønsted sites of BAS are obtained at both PBE + D2 and MP2 + ΔCC level. The results show that MP2 + ΔCC intrinsic energy barriers are higher than corresponding PBE + D2 intrinsic energy barriers about 32–42 kJ/mol. For the primary or secondary carbocation-like transition states, the relative energies decrease with the increase of the carbon number. For the reactant of propene, the conversion into 2-propoxide is energetically more favored than the conversion into 1-propoxide.

Reactivity and reaction pathways of peroxymonosulfate and peroxydisulfate with neonicotinoid insecticides

Neonicotinoid insecticides (NNIs), which have been detected across diverse aquatic environments, have sparked substantial concerns regarding their potential adverse ecological and health risks. In this study, the removal of NNIs by unactivated peroxymonosulfate (PMS) and peroxydisulfate (PDS) was systematically investigated. Results showed that PMS/PDS direct oxidation is mainly responsible for the degradation of imidacloprid (IMD), and the degradation kinetics can be well described by a second-order kinetics model, first-order in both IMD and PMS/PDS concentration. The species-specific reaction rate constants of HSO5− and SO52− with IMD were calculated to be 429.36 ± 15.41 M−1h−1 and 9.72 ± 35.48 M−1h−1, while the corresponding rate constant between S2O82- and IMD is 25.04 ± 3.04 M−1h−1. Over 100 transformation products in the degradation of IMD by PMS/PDS were identified by HPLC/Q-Orbitrap HRMS, and five major reaction pathways were proposed thereafter: hydroxylation on imidazolidine ring, olefin reaction on imidazolidine ring, desnitro reaction on nitroguanidine moiety, and two chain-breaking reactions between imidazolidine ring and chloro-pyridyl moiety. Toxicity evaluation on the transformation products found that their ecotoxicity is various at a wide range with an overall indeterminacy, while their bioconcentration factors show a definite decrease. The reactivity of six NNIs with PMS/PDS was found varied by structures but generally low, indicating that in-situ oxidation with unactivated PMS/PDS is safe but inefficiency for the mitigation of NNIs. It is thus suggested that further investigations into activated PMS/PDS systems involving radicals promise enhanced remediation of NNIs, and fundamental data in this study has laid the groundwork.

Cu‐Catalyzed Intramolecular Borylation‐Cross Coupling Reaction of Unactivated Alkenes to Borylated Indolines

AbstractCu‐catalyzed intramolecular borylation‐cross coupling reaction of alkenes was developed. Racemic and chiral borylated indolines were achieved by borylation‐cross coupling of alkenes with B2pin2 via simultaneous construction of C−C and C−B bonds by Cu/phosphine ligand system. With CuOAc and DPPE ligand, a series of 3‐substituted borylated indoline derivatives were concisely synthesized in good to excellent yields in short time under mild conditions. Asymmetric synthesis was investigated by ligand screening, and the chiral 3‐substituted borylated indoline was obtained in 80% yield and 80:20 er with (R, R)‐Me‐Duphos. Application of 3‐substituted borylated indolines has been demonstrated by a gram scale synthesis and further functionalization.

5-Nitroisoxazoles in SNAr Reactions: A Novel Chemo- and Regioselective Approach to Isoxazole-Based Bivalent Ligands of AMPA Receptors.

An efficient regioselective approach to novel functionalized bis(isoxazoles) with a variety of aromatic and aliphatic linkers was elaborated, based on the heterocyclization reaction of electrophilic alkenes under the treatment with tetranitromethane-triethylamine complex affording 3-EWG-5-nitroisoxazoles. The subsequent SNAr reactions of 5-nitroisoxazoles with various O,O-, N,N- and S,S-bis(nucleophiles) provide a wide range of bis(isoxazole) derivatives in good isolated yields. Employing an elaborated method, a series of novel bis(3-EWG-isoxazoles) as the promising allosteric modulators of AMPA receptors were designed and synthesized. The effect of the compounds on the kainate-induced currents was studied in the patch clamp experiments, revealing modulator properties for several of them. The best positive modulator potency was found for dimethyl 5,5'-(ethane-1,2-diylbis(sulfanediyl))bis(isoxazole-3-carboxylate), which potentiated the kainate-induced currents in a wide concentration range (10-12-10-6 M) with maximum potentiation of 77% at 10-10 M. The results were rationalized using molecular docking and molecular dynamics simulations of modulator complexes with the dimeric ligand-binding domain of the GluA2 AMPA receptor. The predicted physicochemical, ADMET, and PAINS properties confirmed that the AMPA receptor modulators based on the bis(isoxazole) scaffold may serve as potential lead compounds for the development of neuroprotective drugs.

2D MOF with multifunctionalized catalytic sites for one‐pot tandem synthesis of cyclic carbonates from olefins and CO2

AbstractOne‐pot tandem synthesis of cyclic carbonates from olefins and CO2 is becoming one of the most potential strategies to fix CO2 and yield high value chemicals. However, this reaction route is in need of high performing catalysts with multifunctionalized catalytic sites in single material which is still a big challenge in one‐pot community. In this term, we combined dimension reduction and surface modification strategies to fabricate a MOF/metal complex composite, that is, Zr‐BTB/PA‐Co. In this composite, the increased Lewis base sites is capable of boosting the adsorption and activation of CO2, which further acted as nucleophilic groups to activate epoxides, while the 2D matrix offered accessible intrinsic Lewis acid sites. These advantages synergistically led to superior catalytic performance of Zr‐BTB/PA‐Co for catalyzing one‐pot reaction of olefins and CO2 under mild conditions (80°C, 1 bar, 12 h and co‐catalyst/solvent free), and even impressive catalytic activity when using CO2 directly from air.

Heteroatom induced synthesis of FeO-Fe3C confined within F-doped graphene shell for efficient CO2 hydrogenation to light olefins

The non-metal elements (B, P, F, and Se) were introduced to construct mesoporous carbon confined FeO-Fe3C active sites, which were applied for CO2 hydrogenation to light olefins reaction successfully. The evolution of Fe species was extensively studied using in-situ XRD technology and the TGA (Thermogravimetric Analysis) method, revealing that the introduction of F not only triggers the formation of FeF2, which can be easily reduced to Fe0, but also elevates the O vacancy density in FeO, which promotes the adsorption and dissociation of CO2 molecular. The formation of Fe3C active sites within mesoporous carbon channels requires a collaborative effort from various components (such as PTFE (Polytetrafluoroethylene), F127 (Soft template), and PR (Phenolic Resin)). The addition of the K promoter reconstructed the electron-rich active sites, thus playing a crucial role in enhancing the yield of light olefins. The 0.8Fe@0.28F-MC + 0.02K exhibited exceptional activity and stability, resulting in a remarkable CO2 conversion of 42.6 % and a light olefin selectivity of 53.4 %. Furthermore, the catalyst maintained stability over a prolonged period of 100 h. This work sheds deep insight into the synthesis mechanism of the Fe3C active site, providing a simple and efficient preparation strategy of Fe3C confined in F-doped graphene shell that catalytic CO2 hydrogenation to light olefins efficiently.

The Reactions of Alkenes with Phenyl-N-triflylimino-λ3-iodane: Solvent and Oxidant Impact.

The reactions of alkenes with phenyl-N-triflylimino-λ3-iodane PhI=NTf (1) have been studied in different conditions. In methylene chloride, in the presence of N-halosuccinimides, the products of mono and bis-triflamidation were obtained. In MeCN, the product of bromotriflamidation (with NBS) with solvent interception or of bis-triflamidation (with NIS) is formed. The reaction with trans-stilbene in acetonitrile with NBS gave rise to cyclization to 2-methyl-4,5-diphenyl-1-triflyl-4,5-dihydro-1H-imidazole. In contrast, with NIS as an oxidant, both in CH2Cl2 and MeCN, the major product was 2,3-diphenyl-1-triflylaziridine formed in good yield. With NBS, aziridine is also formed but as a minor product, the major one being a mixture of diastereomers of the product of bromotriflamidation. The reaction of compound 1 with vinylcyclohexane in methylene chloride affords the mixtures of regioisomers of the products of halotriflamidation, whereas in acetonitrile, the products of solvent interception and cyclization to the imidazoline are formed. A mechanism explaining the formation of all isolated products is proposed.

Palladium(II)‐Catalyzed Markovnikov Hydroalkynylation of Unactivated Terminal Alkenes†

Comprehensive SummaryAlkynes are versatile synthons in organic synthesis, as well as important structural moieties in bioactive molecules. Recently, transition metal‐catalyzed hydroalkynylation of alkenes has been developed with reactive alkenes and alkenes bearing directing groups. However, the regioselective hydroalkynylation of simple alkenes is still challenging. Herein, we have developed a palladium‐catalyzed Markovnikov hydroalkynylation of unactivated terminal alkenes, which provides an efficient approach for the synthesis of branched alkynyl compounds under mild conditions. This reaction features excellent functional group tolerance, good reaction yields and excellent regioselectivity. Moreover, the asymmetric hydroalkynylation reaction has also been achieved with moderate enantioselectivity by introducing a sterically bulky chiral Pyox ligand.

Intermolecular Carbophosphination of Alkynes with Phosphole Oxides via Ni−Al Bimetal‐Catalyzed C−P Bond Activation

AbstractIntermolecular carbophosphination reaction of alkynes or alkenes with unreactive C−P bonds remains an elusive challenge. Herein, we used a Ni−Al bimetallic catalyst to realize an intermolecular carbophosphination reaction of alkynes with 5‐membered phosphole oxides, providing a series of 7‐membered phosphepines in up to 94 % yield.

Intermolecular Carbophosphination of Alkynes with Phosphole Oxides via Ni-Al Bimetal-Catalyzed C-P Bond Activation.

Intermolecular carbophosphination reaction of alkynes or alkenes with unreactive C-P bonds remains an elusive challenge. Herein, we used a Ni-Al bimetallic catalyst to realize an intermolecular carbophosphination reaction of alkynes with 5-membered phosphole oxides, providing a series of 7-membered phosphepines in up to 94 % yield.

Palladium-catalyzed synthesis of carboxylic acid anhydrides from alkenes

Hydrocarbonylation of alkenes with nucleophiles – water, alcohols and amines, is widely studied and implemented in synthesis of fine chemicals and natural products. Here, an efficient and additive-free palladium-catalyzed hydrocarbonylation reaction of alkenes is described using carboxylic acids as the nucleophile, by which acid anhydrides are obtained in moderate to excellent yields. The relative concentrations of substrate and reagents play an important role in driving the reaction forward, which reaches an equilibrium at equimolar concentrations under a given CO pressure. A ligand-screening study revealed the use of electron-poor phosphine ligands to be crucial for obtaining higher rates of the catalytic reaction. Several substrates including unactivated alkenes were successfully converted to the corresponding symmetric as well as mixed anhydrides. An additional advantage of our synthetic procedure is that the obtained anhydrides can be converted to (primary) amides, thioesters or esters in situ via a simple one-pot derivatization reaction, since acid anhydrides are prone to degradation on isolation.

Visible Light‐Induced [3+2] Annulation Reaction of Alkenes with Vinyl Azides: Direct Synthesis of Functionalized Pyrroles

Comprehensive SummaryA photocatalytic [3+2] annulation of alkenes with vinyl azides was developed under irradiation by visible light in the presence of organic dye photocatalysts. Broad substrate scope and high functional group tolerance were demonstrated by more than 50 examples. The reaction provides a novel and efficient method for the synthesis of polyfunctionalized pyrroles under very mild metal‐free conditions without other additives.

Palladium-Catalyzed Atroposelective Kinetic C-H Olefination and Allylation for the Synthesis of C-B Axial Chirality.

The direct C-H functionalization of 1,2-benzazaborines, especially asymmetric version, remains a great challenge. Here we report a palladium-catalyzed enantioselective C-H olefination and allylation reactions of 1,2-benzazaborines. This asymmetric approach is a kinetic resolution (KR), providing various C-B axially chiral 2-aryl-1,2-benzazaborines and 3-substituted 2-aryl-1,2-benzazaborines in generally high yields with excellent enantioselectivities (selectivity (S) factor up to 354). The synthetic potential of this reaction is showcased by late-stage modification of complex molecules, scale-up reaction, and applications.

Palladium‐Catalyzed Atroposelective Kinetic C−H Olefination and Allylation for the Synthesis of C−B Axial Chirality

AbstractThe direct C−H functionalization of 1,2‐benzazaborines, especially asymmetric version, remains a great challenge. Here we report a palladium‐catalyzed enantioselective C−H olefination and allylation reactions of 1,2‐benzazaborines. This asymmetric approach is a kinetic resolution (KR), providing various C−B axially chiral 2‐aryl‐1,2‐benzazaborines and 3‐substituted 2‐aryl‐1,2‐benzazaborines in generally high yields with excellent enantioselectivities (selectivity (S) factor up to 354). The synthetic potential of this reaction is showcased by late‐stage modification of complex molecules, scale‐up reaction, and applications.